Vacuum-tube circuits



Jan. 3, 1928. I

E. w. KELLOGG VACUUM TUBE CIRCUITS Filed 001;. 5, 1922 2 Sheets-Sheet lfnvenon' Edward W/(e// 9 W- ///'s Attorney Jan. 3, 1928.

E. W. KELLOGG VACUUM TUBE CIRCUITS Filed Oct. 5, 1922 2 Sheets-Sheet 2Inventor-5 Edward Ke// ///Ls Attorney I Patented Jan. 3, 1928.

UNITED STATES PATENT GFFICE.

EDEVARID W. KELLOGG, OF SCHENECTADY, NEW YORK, ASSIGNOE TO GENERAL ELEG-IRIG COMPANY, A CORPORATION 01 NEW YORK.

VACUUM-TUBE CIRCUITS.

Application filed October 5, 1922.

My present invention relates particularly to circuit arrangements foramplifying and detecting high frequency signaling currents by means ofthree eletrode electron discharge devices employingthe principle ofelectro static current control, although it is not limited in itsapplication to this method of control, but may be employed with devicesembodying the electromagnetic principle of current control.

The object of my invention is to provide improved circuit arrangementswhereby the number of separate devices necessary to employ to secure adesired result may be reduced by permitting of the use of a singledevice to serve different functions.

In the heterodyne reception of continuous wave telegraphic signals bymeans of elec tron discharge devices, two general methods have beenemployed known self heterodyne or autodyne and separate heterodyne. Inthe first of these methods a single device has been employed as detectorand generator of local high frequency currents of a frequency differingfrom the signaling frequency. This has necessitated the use of resonantcircuits with the device tuned to a frequency differing from the signalfre quency. As a result the amplification of the signal frequencypossible with such an arrangement has been greatly reduced or entirelyeliminated particularly in the reception of'long waves.

To overcome this disadvantage the separate heterodyne system has beenemployed in which a second device has been used as a generator of localoscillations and the oscillations thus generated have been impressedupon the grid or control circuit of the detector. The grid or controlcircuit of the detector may then be tuned to the signal frequency andamplification of the signal either with or without regeneration may bereadily obtained.

I have discovered that results substantially equal to those obtained bythe separate heterodyne may be obtained with a single device. To securesuch results two separate tuned circuits may be provided in connec tionwith the grid or control circuit of the device and separate feed backconnections employed from the plate circuit for feeding back energy tothese two tuned circuits. As an alternative arrangement, the circuitwhich is tuned to the local frequency may be asso- Sclial No. 592,605.

ciated with the plate circuit and a feed back connection provided fromthis tuned circuit to the grid or control circuit in addition to thefeed back connection employed for regenerative amplification.

It has hertofore been proposed to employ an electron discharge deviceboth for radio and audio frequency signal amplificz'ition. I havediscovered that a device employed for audio frequency amplification mayat the same time be employed as an oscillator for generating the localfrequency oscillations for separate heterodyne reception thus permittingof the use of all of the devices em ployed in a receiving and amplifyingsystem for two purposes. For example, in a system employing threeelectron discharge devices, one device may serve for both radio andaudio frequency amplification, a second device for audio frequencyamplification and generating oscillations, and the third device as adetector and amplifier as in the separate heterodyne system.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inventionitself, however, both as to its organization and method of operationwill best be understood by reference to the following description takenin connection with the accompanying d'awing in which Figs. 1 and 2 showdiagrammatically two different circuits whereby a single device may beemployed as detector, amplifier and oscillator and Figs. 3, 4e and showdiagraimuati- Cally different circuit arrangements in which all of thedevices employed serve double functions.

In the arrangement illustrated in Fig. 1., an electron discharge device1 of the three electrode type is shown. The grid circuit of this deviceincludes a resonant circuit 2 which is tuned to the signal frequency anda second resonant circuit 3 which is tuned to the local frequency to begenerated. A feed-back coupling coil 4- in the plate circuit furnishesenergy to oscillating circuit 3 for generating oscillations and a secondfeed back coupling coil 5 in the plate circuit which is coupled to theantenna coupling coil 6 or to the tuned circuit 2 or both, and permitsof regenerative amplification. The usual grid condenser 7 and grid leak8 cause the device to also function as a detector.

The only reaction between the two tuned circuits, in this, case occurswhen they are tuned alike. At this point the signal circuit finiteimpedance compared with the tuned circuits, and the coils not coupled,there would. be, no reaction between the circuits.

This desirable condition may be approached by making the tuned circuitsof low impedance, i. e., large capacity and low inductance.

In the arrangement shown in Fig.2 a resonant circuit 9 which is tuned tothe local frequency, is connected to the plate circuitand this resonantcircuit is coupled to the coupling coil 10 in the grid circuit. In thiscase also oscillations may be produced with substantially no reactionbetween the two tuned circuits. The grid coil 10 should be of so fewturns that its coupling with the tuned circuit 9v will, under noconditions, bring its impedance up to an appreciable value ascomparedwith the grid impedance.

It will also be found desirable when signal regeneration is employed asindicated in Fig. 2 to use ashunting resistance 11 across the platetuned circuit for the following reason. At resonance the impedance ofthe multiple tuned circuit 9 in series with the plate becomes very high.The result will be a decrease in the signal frequency plate current asthe oscillator setting approaches zero beats and a consequently reducedregeneration and a weakening of the signaling current. There will alsobe a reaction on the amount of signal regeneration by the shift in phaseof the plate current as the plate tuning passes through the point ofmaximum impedance. These effects may be minimizedby making the platetuningof lov impedance as compared'with the plate impedance, either byusing a large capacity and small inductance or by including a portiononly of the inductance in serie with the plate as indicated in Fig. 2.,The use of the resistance 11 in shunt to the portion 12 of theinductance which is in series with the plate also decreases the reactionof the tuning on the plate current. The value of the resistance 11 maybe aboutequal to the value of the plate impedance. A portion of theoscillator frequency plate energy will be wasted by this arrangementbutthis will not be objectionable in this case. By means of the platetuning-as shown in Fig. 2, the plate energy can be'used more'efiiciently than with grid tuning and plate tickler coil as shown inFig. 1. The oscillations inthis case can be maintained with smallamplitude variations on the grid and therefore without choking the tubeor reducing its sensitiveness to the signal.

In Fig. 3 I have shown a continuous wave amplifying and detecting systememploying three tubes 13, 1 1 and 15. Tube 13 is connected as aregenerative amplifier and de tector. The audio frequency currentproduced in the plate circuit of tube 13 is supplied by transformer 16to the grid circuit of tube 14. A tuned circuit 17 in the grid circuitof tube 1d is coupled by coupling 18 to the plate circuit to produce thelocal oscillations which are impressed by means of the coupling 19 uponthe grid circuit of tube 13. Tube 14 thus acts as audio frequencyamplifier and oscillator. The output from the plate circuit of tubeletis supplied by the audio frequency transformer 20 to the grid circuitof tube 15 which thus acts as an audio frequency amplifier. Thereceiving telephones 21 are connected to the plate circuit of tube 15inthe usual manner. Extra windings 22 and 23 may be supplied upon thetransformers 16 and 20 connected to the jacks 2 1 and 25 to permitconnecting the telephone receivers to the output circuits of tubes 13and 141 if desired. The plate circuits of all of the tubes are suppliedwith current from a single source 26. The primary windings oftransformers 16 and 20 are preferably shunted by by-pass condensers 27to permit the passage of high frequency currents flowing in the platecircuits,

In Fig. 1 I have shown a slightly different three tube arrangement. Inthis case tube 29 serves as an oscillator to feed local oscillations tothe grid circuit of tube 30, which acts as a detector, by means of theshielded connecting links 31. The transformer 32 in the plate circuit oftube supplies audio frequency currents to the grid circuit of tube 29causing this tube to also act as audio frequency amplifier as well asoscillator. Audio frequency currents from the plate circuit of tube 29are supplied by transformer 33 to the. grid circuit of tube 3&- andamplified audio frequency currents from the plate circuit of amplifiertube. 3fmay be supplied by transformer 35 and jack 36 to the receivingtelephones. Tube 341- may also be used as a radio frequency amplifier byinserting the plug 87,which is connected to the antenna coupling.circuit 38 in the jack 39 which is connected in the grid circuit of tube3 1. By means of the coupling 40 the-amplified high frequency currentsfrom the plate circuit of tube 3% are supplied to the grid circuit ofdetector tube 30. Ajacl; 41 may also be provided in the grid circuit ofdetector 30 to permit of the impressing of the received signalingcurrents directly upon the grid circuit of the detector.

To prevent undesired reactions between the different stages ofamplification series reactances 42 and shunt condensers 13 willpreferably be employed in the plate supply circuit-s. A low pass filterA is also preferably inserted in the plate circuit of de tector tube 30.

The arrangement shown in Fig. is similar to that shown in Fig. i withthe exception that means is provided in this case whereby tube 29 mayserve both as radio frequency amplifier and audio frequency amplifier,the jack permitting of the impressing of the received signaling currentsdirectly on the grid circuit of tube 29. Tube 34 may serve both as audiofrequency amplifier and radio frequency amplifier as in Fig. f. In casethe arrangement is to be employed for the reception of interruptedcontinuous waves, spark signals or radio telephony, the feed backconnection 46 may be adjusted for regenerative amplification. If thesystem is to be employed for receiving continuous wave telegraphicsignals, the tuning and feed back may be adjusted so that tube 30 servesas a self-heterodyne de tector.

Certain of the novel. features disclosed in Figs. 3, i and 5 of thisapplication are described and claimed in my copending application,Serial No. 712,442, filed May 10, 1924.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The combination in a signal receiving system of an electron dischargedevice having plate and control circuits, two tuned circuits associatedwith said device, one of which is resonant to the signal frequency andthe other to a slightly different frequency, an inductive feed backconnection between plate and control circuits whereby oscillations of aslightly different frequency from the signal frequency may be producedand a second inductive feed back connection between plate and controlcircuits for producing regenerative amplification of the signalingcurrent.

2. The combination in a signal receiving system of an electron dischargedevice having plate and control circuits, two tuned cir cuits connectedin said control circuit, one of which is resonant to the signalfrequency and the other to a slightly different frequency, a feed backconnection between plate and control circuits whereby oscillations of aslightly different frequency from the signal frequency are produced inthe control circuit, and a second inductive feed back connection betweenplate and control circuits for producing regenerative amplification ofthe signaling currents.

3. The combination in a signal receiving system of an electron dischargedevice having plate and control circuits, a tuned circuit connected tothe control circuit which is resonant to the signal frequency, a secondtuned circuit connected to the plate circuit which is resonant to afrequency slightly different from the signal frequency, a feed backconnection from the plate circuit to the resonant circuit which isconnected to the control circuit and an inductive feed back connectionto the control circuit from the resonant circuit connected to the platecircuit.

4t. The combination in a signal receiving system of an electrondischarge device having plate and control circuits, at tuned circuitconnected to the control circuitwhich is resonant to the signalfrequency, a second tuned circuit connected to the plate circuit whichis resonant to a frequency slightly different from the signal frequency,a resistance in shunt to said second tuned circuit, a feed backconnection from the plate circuit to the resonant circuit which isconnected to the control circuit and a feed back connection to thecontrol circuit from the resonant circuit connected to the platecircuit.

5. The combination in a signal receiving system of an electron dischargedevice having plate and control circuits, a tuned circuit connected tothe control circuit which is resonant to the signal frequency, a secondtuned circuit connected to the plate circuit which is resonant to afrequency slightly different from the signal frequency, and a resistancein series in the plate circuit and in shunt to a portion of theinductance of the second tuned circuit.

6. The combination in a signal receiving system of an electron dischargedevice having plate and control circuits, a tuned circuit connected tothe control circuit which is resonant to the signal frequency, a secondtuned current connected to the plate circuit which is resonant to afrequency slightly different from the signal frequency, and resistanceof the same order of magnitude as the plate impedance in series in theplate circuit and in shunt to a portion of the iuductance of the secondtuned circuit.

T. The combination in a signal receiving system of an electron dischargedevice having plate and control circuits, and two independent feed backconnections between said circuits which are external to the electrondischarge device, one of said feed back connections being adapted toproduce oscillations of a radio frequency different from the signalingfrequency, and the second of which is adapted to produce regenerativeamplification of signaling currents and means for detecting beatsproduced by in teraction of the currents of two different frequencies.

8. The combination in a signal receiving system of an electron dischargedevice having plate and control circuits, two tuned circuits associatedtherewith which are resonant to the signal frequency and a radiofrequency differing from the signal frequency,

and two independent feed back connections &

between said circuits Which are external to the electron dischargedevice. one of said feed back connections eing adapted to produceoscillations of a radio frequency diflerent from the signaling frequencyand the second of which is adapted to produce rcgenerative amplificationof signalii'ig currents and means for detecting heats produced byinteraction of the currents of two different frequencies.

9. The combination in a signal receivingsystem of an. electron dischargedevice having plate and control circuits, :1 tuned circuit connected tothe control circuit which is resonant to the signal frcquen'cy a' secondcircuit associated with the device which is resonant to a radiofrequency differing from the signal frequency, and twoindependent feedback connections between said circuits which are external to theelectron discharge device, one of said feed back connections beingadapted to produce oscillations of a radio frequency different from thesignaling frequency and the second of Which is adapted to produceregenerative amplification of signaling currents and means for detectingbeats produced by interaction of the currents of two differentfrequencies.

In itness whereof, I have hereuto set my hand this 4th day of October,1922.

EDlVARD W. KELLO GG.

